Powder paints having aluminum flakes encapsulated in thermosettable material containing tetraalkylammonium halides

ABSTRACT

Improved powder paint compositions providing greater depth variation of metal pigment particles comprise (1) aluminum flakes individually encapsulated in a thin, continuous, thermosettable, organic film-former containing an ammonium salt selected from tetraalkyl ammonium halides and substituted tetraalkylammonium halides wherein at least one alkyl radical is replaced with an aryl, phenoxy or alkoxy radical and (2) a particulate, organic film-former. The encapsulated aluminum flakes are prepared by intimately dispersing the aluminum flakes in a solution of the thermosettable, organic film-former and the ammonium salt in a volatile solvent and spray drying the resultant dispersion. In the preferred embodiment, the particulate, organic film-former is also a thermosettable material and, in the most preferred embodiment, it is also crosslinkable with the thermosettable coating on the aluminum flakes.

RELATION TO PARENT APPLICATION

This application is a Continuation-In-Part of copending U.S. Pat. application Ser. No. 422,474 filed Dec. 6, 1973 under the same title and now abandoned. This application contains the illustrative examples of the parent application and additional illustrative examples wherein the amounts of thermosettable film-forming material deposited on the metal particles prior to their incorporating into a powder paint are above that illustrated in the parent. The recitational disclosures as to the same in the body of the specification are conformed to take into account the additional examples.

BACKGROUND OF THE INVENTION

One basic technique for the manufacture of powder coating materials is the so-called fusion method. This involves the mixing of solvent-free raw materials in their molten state, usually via some form of extruder, cooling, pulverization and size separation-classification. This method has a number of disadvantages unrelated to pigmentation and an additional short-coming when metal flakes are employed as pigments. The high shear employed in the mixing stage results in deformation of the metal flakes. Additionally, during the pulverization step, the metal flakes are further deformed and reduced in particle size. Coatings produced from such powders are characterized by a low level of brilliance and poor polychromatic appearance.

Another basic technique for the manufacture of powder coating materials is the so-called solution-preparation, solvent-separation technique which can be effected by more than one method. This general technique involves the preparation of a coating material in an organic solvent, separation of the solvent from the paint solids, and size-separation classification. Also, pulverization in some form may or may not be required depending upon the solvent separation method involved.

The separation of the solvent can be carried out by conventional spray drying techniques or by heat exchange separation wherein the components of a paint solution are separated by volatilization of the more volatile solvent and separation of the volatilized solvent from the nonvolatilized paint solids by gravitational forces. Since the metal flakes can be added after pulverization, if pulverization is required when using any of the solvent separation methods, damage to the metal flakes during pulverization can be avoided by using the solution preparation-solvent-separation technique. Problems do arise, however, with respect to distribution and orientation of the metal flakes when the powder coating material is applied to the substrate to be coated. This is particularly true when the method of application is that of electrostatic spray, the method most commonly employed to apply the final coating of paint to automobiles and a variety of other metal manufacturers. In such applications, the flakes tend to orient in a random fashion with a low percentage of the flakes parallel to the substrate. The net result is a high degree of metal protusion with little metallic brilliance and a low gloss factor.

Thus, when either of the aforedescribed methods are used to produce metal-pigmented, powder-paint coatings in accordance with the prior art processes, a substantially higher aluminum to non-metal pigment ratio is required, relative to the same ratio in liquid paints, in order to achieve the same degree of brightness and metallic appearance obtained with liquid paints. Further, the problem of metal flake protrusion remains even when brightness and metallic appearance are achieved.

In liquid paints, it is known to partially coat aluminum flakes used as pigments to increase the electrostatic spray efficiency of such paints. In U.S. Pat. No. 3,575,900, a method is disclosed for precipitating the resin of the solution coating upon the aluminum flake in colloidal form. This solution is then used as such or mixed with another solution for use. The patentee specificially points out that, while it may be convenient to call this encapsulation, it is not intended to denote that the aluminum particles are completely enveloped. The resin disclosed for this purpose is a copolymer of vinyl chloride and monoethylenically unsaturated monomers containing about 60 to about 90 percent by weight vinyl chloride. Aluminum flake is also partially coated in U.S. Pat. No. 3,532,662. Here the coating was carried out with a random copolymer of methyl methacrylate and methacrylic acid adsorbed on the pigment. By this method, a dispersion is made of the solid particles in a liquid continuous phase comprising an organic liquid containing in solution a polymer which is adsorbed by the particles and a stabilizer, and modifying the polarity of the continuous phase so that the polymer is insoluble therein, the stabilizer being a compound containing an anchor component which becomes associated with the adsorbed polymer on the particle surface and a pendant, chain-like component which is solvated by the modified continuous phase and provides a stabilizing sheath around the particles. It is alleged that this improves the "wetting" of the treated particles by the film-forming material dispersion-type coating composition.

Powder paints have certain advantages over conventional liquid paints in that they are essentially free of volatile solvents but they also present problems which differ from the problems encountered with liquid paints. These differences include differences with respect to employment of aluminum flakes as a color producing component. For instance, when flakes partially coated by resin precipitate are employed in liquid paints, there remains the organic solvent and other components of the solution to prevent direct exposure of the flake to the atmosphere and other external influences. Further, in powder paints, if aluminum flake is coated, the coating must be a relatively dry solid and the size, weight and continuity of the organic encapsulation are all factors in affecting the distribution of such particles when electrostatically sprayed with the powder that is the principal film-former of the coating composition.

Coated aluminum flakes, i.e., aluminum flakes individually encapsulated in a continuous thermosettable film, admixed with the particulate principal film-former of a powder paint and electrostatically sprayed on a metal substrate will in a substantial portion orient in parallel relationship to the substrate. This substantially reduces or eliminates flake protrusion. Unfortunately, however, there remains a tendency for these coated to assume a substrate - parallel orientation close to the outer surface of the cured coating. This can produce two undesired results. The first of these is an insufficient appearance of metallic depth in the coating wherein the metal flakes are seen through varying depths of a film which is usually colored with a non-metal color producing component. The second is an undesired "silvery" effect which dominates the non-metal color producing component if the concentration of the near-surface, substrate-parallel flakes is too high.

THE INVENTION

A dominance of "silvery" effect in polychromatic finishes resulting from an overabundance of aluminum flakes near and parallel to the outer surface of a cured coating is avoided and depth variation for the metal color producing component in polychromatic or monochromatic finishes is achieved by including a suitable ammonium salt, preferably a tetraalkyl ammonium halide in the thermosettable coating in which the aluminum flakes are encapsulated prior to admixture with the principal film-forming powder. To avoid unnecessary duplication of disclosure, this invention will be described with reference to using the preferred tetraalkyl ammonium halides.

The use of these salts as catalysts and anti-static agents in the principal film-former of a powder coating composition is known from U.S. Pat. Nos. 3,730,930; 3,758,632; 3,758,633; 3,758,634 and 3,758,635. These salts may be used in the principal film-former of the coating compositions of this invention but such use will not achieve the results of this invention. The respective roles of these salts in the encapsulating film and in the principal film-former of the powder composition are quite interesting. It has been discovered that the effective upper limit for the concentration of such salts in the encapsulating film is substantially higher when the principal film former also contains such salts than it is when the principal film-former does not contain such salts. Thus, when the principal film-former of the powder paint composition contains in excess of about 0.05, e.g., 0.05 to about 0.15, weight percent of these salts, the concentration in the encapsulating film may range between about 0.05 to about 20, preferably 0.05 to 10, parts by weight per 100 parts by weight of the thermosettable film-former used to encapsulate the flakes. On the other hand, if the principal film-former is free of such salts, the effective range for employing such salts in the encapsulating film is about 0.05 to about 12 parts by weight per 100 parts by weight of the thermosettable film-former.

The desired depth variation can also be achieved by mixing nickel powder with the encapsulated aluminum flakes in a weight ratio of nickel powder to coated aluminum flakes in a weight ratio of nickel powder to coated aluminum flakes in the range of 1:4 to 5:1. These coating compositions are disclosed in our U.S. Pat. applications Ser. Nos. 506,487 and 506,491 filed of even date with this application. Nickel powder can be used in the coating compositions of this invention when desired. The use of the tetraalkyl ammonium halides in accordance with this invention permits one to reduce the amount of nickel powder used in conjunction with the coated aluminum flakes to achieve a given result. Ordinarily, such reduction will be by a factor of about 1/10.

The preferred tetraalkyl ammonium halides for use in this invention have 1 to 4 carbons in their alkyl groups, e.g., tetramethyl ammonium bromide, chloride and iodide; tetraethylammonium bromide, chloride and iodide; and tetrabutyl ammonium bromide, chloride and iodide. Other suitable ammonium halides which are suitable include the aryl, alkylauryl, aryloxy, and alkoxy substituted tetraalkyl ammonium halides such as dodecyl dimethyl (2-phenoxyethyl) ammonium bromide, chloride and iodide and diethyl (2-hydroxyethyl) methyl ammonium bromide, etc.

In addition one may also use the hydrohalides of mono-, di, and tertiary amines. Another group of additives which can be used are alkyl-poly (ethyleneoxy) phosphates such as, for example, dibutyl-poly (ethyleneoxy) phosphate or alkylauryl poly (ethyleneoxy) phosphates such as, for example, ethyl benzyl poly (ethyleneoxy) phosphate.

Aluminum flakes which are incorporated in powder paints to provide a metallic color producing component are herein encapsulated in a thin, continuous, thermosettable organic coating through which the aluminum particle is visible to the human eye. This coating is preferably transparent but may be translucent. The term "substantially transparent" as used herein means materials which are either transparent or translucent or partially transparent and partially translucent.

As these metal pigments are most frequently used in polychromatic finishes, the powder coating composition will ordinarily contain at least one non-metal color producing component. The "non-metal color producing component" may be a particulate pigment, dye or tint and may be either organic, e.g., carbon black, or inorganic, e.g., a metal salt.

The aluminum color producing component is most often aluminum flakes in the form of aluminum paste. To avoid unnecessary complication of the description of this invention, such aluminum flakes will be used to illustrate the invention. It should be understood, however, that this method is applicable to any particulate aluminum used as a color producing component in a powder coating material. This includes aluminum particles which are solely aluminum, aluminum coated organic particles, and polymer-sandwiched metal particles having exposed metal edges.

In accordance with this invention, the coated metal particles are admixed, i.e., cold blended, with the balance of the coating material after the principal film-former is in particulate form. The non-metal color producing component may be admixed with the film-forming powder before, after or during the addition of the coated metal particles but such component is preferably added before the coated metal particles. This order of mixing avoids degradation of the metal particles in any of the steps of preparing the film-forming powder.

The film-former used to coat the metal particles in accordance with this invention may be the same as or different than the principal film-former of the powder coating material. The film-former used to coat the metal particles is an organic, thermosetting, film-former which may take the form of a self-crosslinkable polymer or a chemically functional polymer and a crosslinking agent reactable therewith. In the preferred embodiment, it is also crosslinkable with the principal film former of the powder coating composition.

The preferred method for coating the aluminum flakes is to disperse the flakes, preferably in the form of aluminum paste, in a small amount of thermosetting organic film-former and a solvent for the film-former that is suitable for spray drying and in which the tetraalkylammonium halide is intimately dispersed. The dispersion is then spray dried by conventional spray drying techniques. Since there is a small amount of film-former relative to the amount of metal flakes, the net result is a metal flake coated with a relatively thin, continuous, coating of the film-former containing the tetraalkylammonium halide as opposed to a metal flake imbedded in a relatively large particle of the film-former.

More specifically, one first disperses the aluminum flakes in about 2 to about 200 weight percent of thermosettable film-former, based on the actual weight of aluminum flakes, i.e., about 2 to about 200 parts by weight of thermosettable film-former per 100 parts by weight aluminum flakes. In one embodiment wherein the coating of such flakes is relatively light, the aluminum flakes are dispersed in about 2 to about 30 weight percent of thermosettable film-former based on the actual weight of the aluminum flakes, i.e., about 2 to about 30 parts by weight of thermosettable film-former per 100 parts by weight aluminum flakes. In most applications, it will be found advantageous to use between 10 and 200, preferably between about 30 and about 70, parts by weight of thermosettable film-former per 100 parts by weight aluminum flakes. When metal particles of different density are used, the weight of aluminum flakes of the same surface area can be used to determine the amount of film-former to use in coating the metal particles. When less than about 2 weight percent of the film-former is used, complete encapsulation of the metal flakes may not result. When more than about 30 weight percent of the film-former is used, care must be taken in controlling the spray drying operation to minimize the formation of an excessive amount of spherical particles containing more than one metal flake. The incidence of full coverage is high in the 30 to 70 range above described. Such spherical particles can be removed from the other coated aluminum flakes by screening. The inclusion of large, multileafed particles in a cured coating provides an irregular appearance. A similar result may be obtained if one mixes the uncoated metal flakes with the principal film-former of a powder paint while the latter is in liquid state and then removes the solvent.

Aluminum paste is aluminum flakes, usually about 60 to about 70 weight percent, in a smaller amount, usually about 30 to about 40 weight percent, of a liquid hydrocarbon solvent which serves as a lubricant, e.g., mineral spirits. A small amount of an additional lubricant, e.g., stearic acid, may be added during the milling operation which produces the aluminum flakes. Everett J. Hall is credited with originating the method of beating aluminum into fine flakes with polished steel balls in a rotating mill while the flakes are wet with a liquid hydrocarbon. See U.S. Pat. No. 1,569,484 (1926). A detailed description of aluminum paste, its manufacture, flake size, testing, uses in paint, etc. is found in Aluminum Paint and Powder, J. D. Edwards and Robert I. Wray, 3rd Ed. (1955), Library of Congress Catalog Card Number: 55-6623, Reinhold Publishing Corporation, 430 Park Avenue, New York, New York, U.S.A. and the same is incorporated herein by reference.

The film-former used to coat the aluminum flakes may be a self-crosslinking polymer or copolymer or a chemically functional polymer or copolymer and a monomeric crosslinking agent. The preferred film-formers for this purpose include thermosettable copolymer systems comprising: (a) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor a C₄ - C₂₀, saturated, straight chain, aliphatic, dicarboxylic acid crosslinking agent-exemplified by U.S. Pat. application Ser. No. 172,236 filed Aug. 16, 1971, now U.S. Pat. No. 3,752,870: (b) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor a mixture of about 90 to 98 percent by equivalent weight of a C₄ - C₂₀, saturated, straight chain, aliphatic dicarboxylic acid and about 10 to about 2 percent by equivalent weight of a C₁₀ - C₂₂, saturated straight chain, aliphatic, monocarboxylic acid-exemplified by U.S. Pat. No. 3,730,930; (c) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor a diphenol having a molecular weight in the range of about 110 to about 550 - exemplified by U.S. patent application Ser. No. 172,228 filed Aug. 16, 1971, now U.S. Pat. No. 3,758,634; (d) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor a carboxy terminated polymerexemplified by U.S. Pat. application Ser. No. 172,229 filed Aug. 16, 1971, now U.S. Pat. No. 3,781,380; (e) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent a phenolic hydroxy terminated polymer - exemplified by U.S. Pat. application Ser. No. 172,225 filed Aug. 16, 1971, now U.S. Pat. No. 3,787,520; (f) an epoxy-functional, carboxy-functional, self-crosslinkable copolymer of ethylenically unsaturated monomers - exemplified by U.S. Pat. application Ser. No. 172,238 filed Aug. 16, 1971, now U.S. Pat. No. 3,770,848; (g) a hydroxy-functional, carboxy-functional copolymer of monoethylenically unsaturated monomers - exemplified by U.S. Pat. application Ser. No. 172,237 filed Aug. 16, 1971, now U.S. Pat. No. 3,787,340; (h) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor an anhydride of a dicarboxylic acid - exemplified by U.S. Pat. application Ser. No. 172,224 filed Aug. 16, 1971, now U.S. Pat. No. 3,781,379; (i) a hydroxy-functional copolymer of monoethylenically unsaturated monomers and as crosslinking agent therefor a compound selected from dicarboxylic acids, melamines, and anhydrides - exemplified by U.S. Pat. application Ser. No. 172,223 filed Aug. 16, 1971 and abandoned in favor of continuation application Ser. No. 407,128 filed Oct. 17, 1973 in turn abandoned in favor of continuation-in-part application Ser. No. 526,547 filed Nov. 25, 1974; (j) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor a compound containing tertiary nitrogen atoms - exemplified by U.S. Pat. application Ser. No. 172,222 filed Aug. 16, 1971, now U.S. Pat. No. 3,758,635; (k) a copolymer of an alpha-beta unsaturated carboxylic acid and an ethylenically unsaturated compound and as crosslinking agent therefor an epoxy resin having two or more epoxy groups per molecule - as exemplified in U.S. Pat. application Ser. No. 172,226 filed Aug. 16, 1971, now U.S. Pat. No. 3,758,633; (1) a self-crosslinkable, epoxy-functional, anhydride-functional copolymer of olefinically unsaturated monomers - exemplified by U.S. Pat. application Ser. No. 172,235 filed Aug. 16, 1971, now U.S. Pat. No. 3,758,632; (m) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor a carboxy terminated polymer, e.g., a carboxy terminated polymer, e.g., a carboxy terminated polyester, - exemplified by application Ser. No. 223,746 filed Feb. 4, 1972 and now abandoned in favor of continuation-in-part application Ser. No. 489,271 filed Aug. 5, 1974; (n) an epoxy-functional copolymer of vinyl monomers and as crosslinking agent therefor a dicarboxylic acid - exemplified by U.S. Pat. application Ser. No. 228,262 filed Feb. 22, 1972, now U.S. Pat. No. 3,787,521; (o) an epoxy-functional and hydroxy-functional copolymer of monovinyl monomers and as crosslinking agent therefor a C₄ - C₂₀, saturated, straight chain, aliphatic dicarboxylic acid - exemplified by U.S. Pat. application Ser. No. 394,874 filed Sept. 6, 1973 and now abandoned in favor of application Ser. No. 552,676 filed Feb. 24, 1975; (p) an epoxy-functional copolymer of monovinyl monomers with optional hydroxy and/or amide functionality and as crosslinking agent therefore (1) a C₄ - C₂₀, saturated, straight chain, aliphatic dicarboxylic acid and (2) a polyanhydride - exemplified by U.S. Pat. application Ser. No. 344,881 filed Sept. 6, 1973 and now abandoned in favor of continuation-in-part Ser. No. 552,556 and continuation-in-part Ser. No. 552,557, both filed Feb. 24, 1975; (q) an epoxy-functional amide-functional copolymer of monovinyl monomers and as crosslinking agent therefor an anhydride of a dicarboxylic acid - exemplified by U.S. Pat. application Ser. No. 394,880 filed Sept. 6, 1973 and now abandoned in favor of application Ser. No. 552,572 filed Feb. 24, 1975; (r) an epoxy-functional, hydroxy-functional copolymer of monovinyl monomers and as crosslinking agent therefore an anhydride of a dicarboxylic acid - exemplified by U.S. Pat. application Ser. No. 394,879 filed Sept. 6, 1973 and now abandoned in favor of application Ser. No. 552,511 filed Feb. 24, 1975; (s) an epoxy-functional, amide-functional copolymer of monovinyl monomers and as crosslinking agent therefore a carboxy-terminated polymer - exemplified by U.S. Pat. application Ser. No. 394,875 filed Sept. 6, 1973 and now abandoned in favor of application Ser. No. 552,518 filed Feb. 24, 1975; (t) an epoxy-functional copolymer of monovinyl monomers and as crosslinking agent therefore a monomeric or polymeric anhydride and a hydroxy carboxylic acid - exemplified by U.S. Pat. application Ser. No. 394,878 filed Sept. 6, 1973 and now abandoned in favor of application Ser. No. 552,079 filed Feb. 24, 1975; (u) an epoxy-functional, amide-functional copolymer of monovinyl monomers and as crosslinking agent therefore a monomeric or polymeric anhydride and a hydroxy carboxylic acid - exemplified by U.S. Pat. application Ser. No. 394,877 filed Sept. 6, 1973 and now abandoned in favor of continuation-in-part application Ser. No. 552,078 filed Feb. 24, 1975; and (v) an epoxy-functional, hydroxy-functional copolymer of monovinyl monomers and as crosslinking agent therefore a monomeric or polymeric anhydride and a hydroxy carboxylic acid - exemplified in U.S. Pat. application Ser. No. 394,876 filed Sept. 6, 1973 and now abandoned in favor of continuation-in-part application Ser. No. 552,077 filed Feb. 24, 1975.

The disclosures of the aforementioned patents and patent applications are incorporated herein by reference.

The term "vinyl monomer" as used herein means a monomeric compound having in its molecular structure the functional group ##EQU1## wherein X is a hydrogen atom or a methyl group.

Other thermoset film-formers suitable for use in coating the metal particles include, but not by way of limitation thermosettable systems in which the polymeric component is a polyester, a polyepoxide and urethane-modified polyesters, polyepoxides and acrylics. As with the acrylics heretofore more specifically described, these may be self-crosslinking polymers or may be a combination of functional polymer and a coreactable monomeric compound which serves as crosslinking agent.

The preferred thermosettable powder paints known to applicants for automotive topcoats, the use wherein metallic pigments find their greatest use, consist essentially of an epoxy-functional copolymer of olefinically unsaturated monomers and a crosslinking agent therefor. Such paints, exclusive of pigments, may also contain flow control agents, catalysts, etc. in very small quantities.

The copolymer referred to in the preceding paragraph has average molecular weight (M_(n)) in the range of about 1500 to about 15,000 and glass transition temperature in the range of about 40°C. to about 90°C. The epoxy functionality is provided by employing a glycidyl ester of a monoethylenically unsaturated carboxylic acid, e.g., glycidyl acrylate or glycidyl methacrylate, as a constituent monomer of the copolymer. This monomer should comprise about 5 to about 20 weight percent of the total. Additional functionality, e.g., hydroxy functionality or amide functionality, may also be employed by inclusion of a C₅ - C₇ hydroxy acrylate or methacrylate, e.g., hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxy propyl acrylate, or hydroxypropyl methacrylate, or an alpha-beta olefinically unsaturated amide, e.g., acrylamide or methacrylamide, among the constituent monomers. When such additional functionality is used, the monomers providing it comprise about 2 to about 10 weight percent of the constituent monomers. The balance of the copolymer, i.e., about 70 to about 93 weight percent of the constituent monomers, are made up of monofunctional, olefinically unsaturated monomers, i.e., the sole functionality being ethylenic unsaturation. These monofunctional, olefinically unsaturated monomers are, at least in major proportion, i.e., in excess of 50 weight percent of the constituent monomers, acrylic monomers. The preferred monofunctional acrylic monomers for this purpose are esters of C₁ - C₈ monohydric alcohols and acrylic or methacrylic acid, e.g., methyl methacrylate, ethyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate and 2-ethylhexyl acrylate. In this preferred embodiment, the remainder, if any, aside from the aforementioned epoxy, hydroxy and amide functional monomers which also have olefinic unsaturation functionality used up in the polymerization formation of the copolymer, is preferably made up to C₈ - C₁₂ monovinyl hydrocarbons, e.g., styrene, vinyl toluene, alpha methyl styrene and tertiary butyl styrene. Other vinyl monomers which are suitable in minor amounts, i.e., between 0 and 30 weight percent of the constituent monomers, include vinyl chloride, acrylonitrile, methacrylonitrile, and vinyl acetate.

The crosslinking agents employed with the aforedescribed copolymer will have functionality that will react with the functionality of the copolymer. Thus, all of the crosslinking agents heretofore mentioned in the recital of powder paint patents and patent applications, e.g., C₄ - C₂₀ saturated, aliphatic dicarboxylic acids, mixtures of C₄ - C₂₀ saturated aliphatic dicarboxylic acids and monocarboxylic acids of carbon number in the same range, carboxy terminated copolymers having molecular weight (M_(n)) in the range of 650 to 3000, monomeric anhydrides preferably anhydrides having a melting point in the range of about 35° to 140°C., e.g., phthalic anhydride, maleic anhydride, cyclohexane-1,2-dicarboxylic anhydride, succinic anhydride, etc., homopolymers of monomeric anhydrides, and mixtures of such anhydrides and hydroxy acids having a melting point in the range 40° to 150°C., are suitable for use as crosslinking agents for these copolymers. The disclosures of all patents and patent applications recited herein are incorporated herein by reference. In general, these crosslinking agents are employed in amounts such as to provide between about 0.3 and about 1.5, preferably between about 0.8 and about 1.2, functional groups which are reactable with functional groups on the copolymer per functional groups on the copolymer.

The best acrylic, thermoplastic, powder coatings known to applicants are copolymers of alpha-beta olefinically unsaturated monomers. These are made up either solely or predominantly of acrylic monomers, i.e., acrylates, methacrylates, mixtures of acrylates and methacrylates and a small fraction of acrylic or methacrylic acid. In the embodiment wherein the copolymer is made up predominantly of acrylic monomers, i.e., in excess of 51 weight percent acrylic monomers, the acrylic monomers may include up to about 5 weight percent acrylic acid, methacrylic acid or a mixture of acrylic acid methacrylic acids while the balance is made up of C₈ - C₁₂ monovinyl hydrocarbons, e.g., styrene, vinyl toluene, alpha methyl styrene, and tertiary butyl styrene. The acrylates and methacrylates used in either of these embodiments are preferably esters of a C₁ - C₈ monohydric alcohol and acrylic acid or methacrylic acid or a mixture of acrylic and methacrylic acids. Thus, such a copolymer would contain about 46 to about 100 weight percent of esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acid, 0 to about 49 weight percent of C₈ - C₁₂ monovinyl hydrocarbons, and 0 to about 5 weight percent acrylic or methacrylic acid with the sum of the aforementioned esters and acrylic or methacrylic acid comprising in excess of 51 weight percent of the comonomers as stated earlier in this paragraph. One such copolymer contains about 76 to about 81 mole percent methyl methacrylate 1 to 3 mole percent acrylic acid or methacrylic acid or a mixture of acrylic and methacrylic acids, and 16 to 23 mole percent butyl methacrylate.

"Alpha-beta unsaturation" as used herein includes both the olefinic unsaturation that is between two carbon atoms which are in the alpha and beta positions relative to an activating group such as a carboxyl group, e.g., the olefinic unsaturation of maleic anhydride, and the olefinic unsaturation between the two carbon atoms which are in the alpha and beta positions with respect to the terminus of an aliphatic carbon-to-carbon chain, e.g., the olefinic unsaturation of acrylic acid, methyl methacrylate or styrene.

DETAILED DESCRIPTION OF THE INVENTION

The preparation of the coated metal flakes is carried out in a solvent for the film-former that is sufficiently volatile for efficient spray drying and which will not chemically react with either the film-former or the metal flakes to a degree that will significantly modify their properties or appearance within the contact timer employed to carry out the spray drying process. A preferred solvent for this purpose is methylene chloride. Other solvents which can be used include toluene, xylene, methyl ethyl ketone, acetone and low boiling petroleum naphthas.

A typical formulation for the feed stock for the spray drier in accordance with this invention would include the following:

                    Parts by Weight                                                ______________________________________                                         aluminum paste    30.00                                                        film former       2.00                                                         MeCl.sub.2        200.00                                                       ______________________________________                                    

Typical operating parameters for a convention, 3 ft. diameter spray drier equipped with a conventional two-fluid nozzle atomizer, e.g., a glass and a liquid as in a convention air stomixing (liquid) paint spray gun are as follows:

    air flow          197 cubic feet/minute                                        feed flow         380 ml/min.                                                  inlet air temperature                                                                            180°F.                                                outlet air tempera-                                                             ture             80°F.                                                 product rate      6 lbs./hr.                                              

The coated aluminum, as received from the spray drier, is then sieved through a screen of desired particulate size, e.g., a 44 micron screen, to remove excessively large particles. Approximately 20 percent of the product in the form of oversize particles is discarded.

The non-metal powder component, hereinafter called the "powder component" comprises the primary film-forming component and where the finish is to be polychromatic, at least one metal color producing component. This non-metal color producing component may be a pigment, dye or tint. For purposes of this invention, white and black shall be considered colors inasmuch as a light reflecting or light absorbing material must be added to the organic film-former to provide the finish with a white or black appearance in the same manner that a material must be added to the organic film-former which reflects light rays that convey to the eye one color while absorbing others.

The film-forming component of the powder component is preferably a thermosetting film-forming material. Those thermosetting film-forming materials heretofore disclosed for use in coating the metal leaves are suitable for use as the principal film-former of the powder component. The thermosets preferred for the coating of the metal leaves are also the preferred thermosets for this purpose.

In addition, the principal film-former of the powder component of this invention may be a thermoplastic powder, e.g., a thermoplastic acrylic polymer having a molecular weight (M_(n)) in the range of 30,000 to 80,000 and a glass transition temperature in the range of 60°C. to 110°C. - as exemplified by U.S. Pat. application Ser. No. 172,227 filed Aug. 16, 1971. These coated flakes, of course, can be used with any thermoplastic powder suitable for use as the principal film-former of any thermoplastic powder paint.

The formulation of the non-metal powder component, which in the case of a polychromatic finish contains a nonmetal color producing component, is prepared taking into consideration the particular color chosen for employment with the metallic color component and the amount of the metallic color component to be employed. The powder component is quantitatively formulated taking into account the amount of material to be brought in through the addition of the coated metal particles.

A typical composition for the powder component is as follows:

                      Parts by Weight                                              ______________________________________                                         film-former         94.33                                                      flow control additive                                                                              0.67                                                       pigment             5.00                                                       ______________________________________                                    

The preparation and processing of the non-metal powder component into powder form is carried out by one of the conventional powder preparation techniques, e.g., extrusion, spray drying, or solvent extraction. Once in powdered form, this material is sieved through a suitable screen, e.g., a 74 micron screen.

The final step in the preparation of the powder coating material of this invention is the blending of the two major components, i.e., the thermoset, organic coated particulate metal component and the non-metal powder component. The exact proportions of the two major components will, of course, depend on the specific formulation and the amount of metal needed. In the typical example aforedescribed, if one blends about 98.5 parts by weight of the non-metal powder component with about 1.5 parts by weight of the coated aluminum, a "low metallic" automotive topcoat paint results.

Appearance of the finished coating will, of course, be a primary factor in selecting the total concentration of aluminum flakes in the total powder paint composition. This concentration will vary from a very low weight percent of the total powder paint composition in some polychromatic finishes, i.e., as low as about 0.005 weight percent, to a much higher weight percent of the total powder paint composition in the so-called "Argent" finishes, i.e., as high as about 25 weight percent when aluminum is the only metal used. If for example, the spray dried coating on the flakes comprises about 2 to about 30 weight percent by weight of the flakes then, the total metal component of the powder paint composition will comprise between about 0.005 to about 32.50, advantageously between about 0.25 to about 28.75, and preferably between about 0.54 to about 28.25, weight percent of the total powder paint composition. These figures will be modified by the weight of nickel powder substituted for a portion of the aluminum. The principal film-forming powder and non-metal pigment, if any, will make up the balance of the powder paint composition. The non-metal pigment will constitute between 0 and about 22 weight percent of the total composition.

This invention will be more fully understood from the following illustrative examples.

EXAMPLE 1 a. Preparation of The Coated Aluminum Flakes

A powder paint in accordance with this invention is prepared from the following materials using the procedures hereinafter outlined:

1. Preparation of an epoxy-functional acrylic copolymer of vinyl monomers is prepared as follows:

    Ingredients         Parts By Weight                                            ______________________________________                                         glycidyl methacrylate                                                                              15                                                         methyl methacrylate 45                                                         butyl methacrylate  40                                                         ______________________________________                                    

The above named ingredients are mixed together. Three parts by weight of 2,2' - azobis - (2-methyl-propionitrile), hereinafter called AIBN, is dissolved in the monomer mixture. The mixture is slowly added to refluxing toluene (100 parts) which is stirred vigorously under a nitrogen atmosphere. A condenser is provided at the top of the toluene container to condense the toluene vapors and return them to the container. The monomer mixture is added through a regulating valve and the rate of addition is controlled to maintain a reflux temperature (109°C. - 112°C.) with only a small fraction of heat supplied from an external heater. After the addition of the monomer mixture is complete, the refluxing is maintained by external heat source for 3 additional hours.

The solution is poured into shallow stainless steel trays. These trays are placed in a vacuum oven and the solvent evaporated therefrom. As the solvent is removed, the copolymer solution becomes more concentrated. The temperature of the vacuum oven is raised to about 110°C. Drying is continued until the solvent content of the copolymer is below 3 percent. The trays are cooled and the copolymer collected and ground to pass through 20 mesh screen. The copolymer has a glass transition temperature of 53°C. and a molecular weight (M_(n)) of 4000.

One hundred parts by weight of the ground copolymer are mixed with the following materials:

                         Parts By Weight                                           ______________________________________                                         azelaic acid           10.0                                                    tetrabutyl ammonium bromide                                                                           0.2                                                     poly (lauryl acrylate)(M.sub.n =10,000)                                                               0.5                                                     ______________________________________                                    

The materials are mixed together in a ball mill for 2 hours. The mixture is mill rolled at 85°C. to 90°C. for 5 minutes. The solid obtained is ground in a ball mill and the powder is sieved with a 140 mesh screen.

Two parts by weight of this thermosettable mixture are combined with 30 parts by weight of aluminum paste (35 percent by weight mineral spirits and 65 percent by weight aluminum flakes that will pass through a 325 mesh screen and have typical surface area of 7.5 m² /g, maximum particle diameter below 45 microns and most common particle size distribution in the range of about 7 to about 15 microns) and 200 parts by weight of methylene chloride under low shear agitation so as to disperse the aluminum in the thermosettable material without damage to the aluminum flakes.

Once the above dispersion has been prepared, it is spray dried in a manner which will produce individual aluminum flakes coated with a thin, continuous coating of dry copolymer containing the tetrabutyl ammonium bromide. This is accomplished in a 3 foot diameter spray drier equipped with a two-fluid nozzle in counter-current position using the following conditions:

    air flow in drying chamber                                                                         200 cubic feet/minute                                      feed rate of mixture                                                                               380 ml/minute                                              inlet air temperature                                                                              180°F.                                              two fluid atomization air pressure                                                                  80 lbs.                                              

The product obtained from this process has an overall composition of 19.5 parts by weight of aluminum and 2.0 parts by weight of the thermosettable mixture aforedescribed plus a small amount of residual solvent (i.e., 0.05 to 0.2 parts) that has not completely volatilized during the spray dry process. This product is then screened through a 44 micron screen.

b. Preparation of the Non-Metal Powder Component

A thermosettable material is produced by mixing 166 parts by weight of the epoxy-functional copolymer employed in the thermosettable material used to coat the aluminum flakes in (a) above with the following materials:

                       Parts By Weight                                             ______________________________________                                         azelaic acid         22.65                                                     poly (lauryl acrylate)                                                                              1.34                                                      phthalo green pigment                                                                               1.75                                                      yellow iron oxide pigment                                                                           8.26                                                      ______________________________________                                    

A homogeneous mixture of the above is obtained by ball milling for 2 hours. This mixture is then extruded at 100°C. from a kneading extruder. The solid thus obtained is pulverized in an impact mill, i.e., an air classified impact mill, and sieved through a 200 mesh screen.

c. Preparation of the Powder Coating Material

A powder coating material in accordance with this invention is produced by mixing 1.65 parts by weight of the coated aluminum flakes with 98.35 parts of the non-metal powder component. A homogeneous mixture of the two components is obtained by rapidly tumbling the material in a partially filled container for 20 minutes, under ambient room conditions, i.e., 65° - 75° F.

It will be noted that in this example the thermosettable material used to coat the aluminum flakes and the thermosettable material used to form the non-metal powder component component are crosslinkable with each other.

The powder thus obtained is then sprayed on an electrically grounded steel substrate with a conventional electrostatic powder spray gun operating at about 50 KV charging voltage. After spraying, the coated substrate is heated to about 350°F. for about 25 minutes. The coating thus obtained has good gloss, good aluminum particle orientation, and good aluminum particle depth. It is resistant to weathering and suitable for automotive top coat application. The coating thus obtained demonstrates a more random metal particle orientation with respect to depth and increased polychromatic light reflection of the cured film than is obtained when this process is duplicated except for omitting the tetrabutylammonium bromide in the coating of the aluminum flakes.

EXAMPLE 2

A powder coating material is prepared following the procedure of Example 1 with the following differences: (1) The coated aluminum flakes are prepared from the following materials.

    ______________________________________                                                                 Parts                                                                          By by Weight                                           ______________________________________                                         aluminum paste            30.000                                                (65% aluminum flakes and                                                       35% mineral spirits)                                                          thermosettable mixture    0.218                                                 (same epoxy-functional copolymer                                               used in example 1 in amount as                                                 195 parts by weight and poly                                                   (azelaic anhydride) .023 parts by weight                                      triethylbenzylammonium chloride                                                                          0.02                                                 poly (lauryl acrylate) (M.sub.n =10,000)                                                                 0.001                                                methylene chloride        197.000                                              ______________________________________                                    

The product obtained after spray drying has a composition of 19.50 parts by weight aluminum, 0.218 parts by weight thermosettable material, 0.02 parts by weight triethylbenzylammonium chloride, and 0.001 parts by weight poly (lauryl acrylate).

The coated aluminum thus produced in the amount of 1.52 parts by weight is combined with 98.48 parts by weight of the non-metal powder component of Example 1 to yield a powder which, excluding the triethylbenzylammonium chloride, has the following composition:

                       Parts By Weight                                             ______________________________________                                         aluminum (dry)       1.50                                                      thermosettable film-former                                                                          92.91                                                      (a) epoxy-functional                                                             copolymer     81.74                                                          (b) azelaic acid   11.15                                                       (c) poly (azelaic                                                                anhydride)     0.02                                                         poly (lauryl acrylate)                                                                              0.66                                                      phthalo green        0.86                                                      yellow iron oxide    4.05                                                      ______________________________________                                    

This powder coating material is electrodeposited upon a metal substrate and heat cured as in Example 1. The resulting coating demonstrates good gloss, metallic orientation, good aluminum flake depth variation and weathering resistance.

EXAMPLE 3

A powder coating material is prepared following the procedure of Example 1 with the following differences:

1. The starting mixture for preparation of the coated aluminum flakes is of the following composition:

                         Parts By Weight                                           ______________________________________                                         aluminum paste         30.00                                                    (65% by weight aluminum and                                                    35% by weight mineral spirits)                                                thermosettable mixture 5.46                                                     (a) epoxy-functional copolymer                                                  4.88Example 1                                                                 (b) poly (azelaic                                                                0.58dride)                                                                  tetramethylammonium bromide                                                                           0.02                                                    poly (lauryl acrylate) 0.03                                                    methylene chloride     250.00                                                  ______________________________________                                    

This material is mixed and spray dried as in Example 1 and in the resultant material the flakes have coating about 2.5 times thicker than that of the coated flakes of Example 1. The empirical composition of the spray dried product, excluding the tetramethylammonium bromide, is as follows:

                       Parts By Weight                                             ______________________________________                                         aluminum (uncoated basis)                                                                           19.5                                                      thermosettable material                                                                             5.46                                                       (a) epoxy copolymer of                                                          4.88mple  1                                                                   (b) poly (azelaic an-                                                            hydride)      0.58                                                          poly (lauryl acrylate)                                                                              0.03                                                      ______________________________________                                    

2. Since the amount of coating on the aluminum flakes is here large enough to be a significant factor, it is taken into consideration when formulating the non-metal powder component. Here, the non-metal powder component is prepared by combining 166 parts by weight of the ground epoxy-functional copolymer of Example 1 with the following:

                       Parts By Weight                                             ______________________________________                                         azelaic acid         22.64                                                     poly (lauryl acrylate)                                                                              1.33                                                      phthalo green pigment                                                                               1.80                                                      yellow iron oxide    8.23                                                      ______________________________________                                    

Subsequent processing of the non-metal powder component is the same as in Example 1.

3. In the blending of the coated metal component and the non-metal powder component, the ratio of coated aluminum to non-metal powder component is altered because of the thickness of coating of the aluminum flakes. The ratio here is 1.93 parts by weight of coated aluminum with 98.08 parts by weight of the non-metal powder component. The resultant powder coating maintains the pigment level essentially the same as in Example 1.

EXAMPLE 4

The procedure of Example 1 is repeated except for the difference that the amount of tetrabutylammonium bromide dispersed in the methylene chloride is such as to provide in the spray dried coatings on the aluminum flakes an average concentration of 0.5 parts by weight of tetrabutylammonium bromide per 100 parts by weight of the thermosettable organic film-former.

EXAMPLE 5

The procedure of Example 1 is repeated except for the difference that the amount of tetrabutylammonium bromide dispersed in the methylene chloride is such as to provide in the spray dried coatings on the aluminum flakes an average concentration of 10 parts by weight of tetrabutylammonium bromide per 100 parts by weight of the thermosettable organic film-former.

EXAMPLE 6

The procedure of Example 1 is repeated except for the differences that the non-metal powder component contains tetrabutylammonium bromide in the amount of 0.14 weight percent and the thermosettable coatings on the aluminum flakes contain tetrabutylammonium bromide in the average amount of 20 parts by weight per 100 parts by weight of thermosettable, organic, film-former.

EXAMPLE 7

The procedure of Example 1 is repeated except for the differences that the non-metal powder component contains tetrabutylammonium bromide in the amount of 0.07 parts by weight and the thermosettable coating on the aluminum flakes contain tetrabutylammonium bromide in the average amount of 10 parts by weight per 100 parts by weight of thermosettable, organic, film-former.

EXAMPLE 8

The procedure of Example 1 is repeated except for the differences that the non-metal powder component contains tetrabutylammonium bromide in the amount of 0.05 weight percent and the thermosettable coating on the aluminum flakes contains tetrabutylammonium bromide in the average amount of 1 part by weight per 100 parts by weight of thermosettable, organic, film-former.

EXAMPLE 9

The procedure of Example 8 is repeated except for the difference that an equivalent amount of tetrabutylammonium chloride is substituted for the tetrabutylammonium bromide.

EXAMPLE 10

The procedure of Example 8 is repeated except for the difference that an equivalent amount of tetrabutylammonium iodide is substituted for the tetrabutylammonium bromide.

EXAMPLE 11

The procedure of Example 8 is repeated except for the difference that an equivalent amount of tetramethylammonium bromide is substituted for the tetrabutylammonium bromide.

EXAMPLE 12

The procedure of Example 8 is repeated except for the differences that the non-metal powder component contains 1 weight percent of dodecyl dimethyl (2-phenoxyethyl) ammonium bromide in lieu of the tetrabutylammonium bromide and the thermosettable coatings on the aluminum flakes contain, in lieu of the tetrabutylammonium bromide, dodecyl dimethyl (2-phenoxyethyl) ammonium bromide in the average amount of 5 parts by weight per 100 parts by weight of the thermosettable film-former.

EXAMPLE 13

The procedure of Example 8 is repeated except for the differences that the non-metal powder component contains 1 weight percent of diethyl (2-hydroxyethyl) methyl ammonium bromide in lieu of the tetrabutylammonium bromide and the thermosettable coatings on the aluminum flakes contain, in lieu of the tetrabutyl ammonium bromide, diethyl (2-hydroxyethyl) methyl ammonium bromide in the average amount of 3 parts by weight per 100 parts by weight of the thermosettable film-former.

EXAMPLE 14

The procedure of Example 8 is repeated except for the differences that the non-metal powder component contains 0.1 weight percent tetrabutylammonium bromide and the coatings on the aluminum flakes contain tetrabutylammonium bromide in the average amount of 12 parts by weight per 100 parts by weight of the thermosettable film-former.

EXAMPLE 15

The procedure of Example 1 is repeated except for the difference that the coated aluminum flakes are replaced with an equal volume of a mixture of nickel powder and coated aluminum flakes prepared in the same manner as those used in Example 1 and containing the same concentration of tetrabutylammonium bromide contained in the coated flakes of Example 1. The weight ratio of nickel powder to coated aluminum flakes in this example is 1.5 to 1.

EXAMPLE 16

The procedure of Example 15 is repeated except for the difference that the weight ratio of nickel powder to coated aluminum flakes is 2.5:1.

EXAMPLE 17

The powder coating material is prepared following the procedure of Example 1 with the following differences: (1) the coated aluminum flakes are prepared from the following materials:

                       Parts By Weight                                             ______________________________________                                         aluminum paste         30.000                                                   (65% aluminum flakes and                                                        35% mineral spirits)                                                         thermosettable mixture 0.218                                                    (same epoxy-functional co-                                                      polymer used in Example 1                                                      in amount as 0.195 parts by                                                    weight and poly (azelaic an-                                                   hydride) 0.023 parts by weight                                               tetrabutylammonium bromide                                                                            0.021                                                   poly (lauryl acrylate) 0.001                                                    (M.sub.n = 10,000)                                                            methylene chloride     197.000                                                 ______________________________________                                    

The coated aluminum product obtained after spray drying in the amount of 1.52 parts by weight are combined with 98.48 parts by weight of the non-metal powder component of Example 1. This powder coating material is electrodeposited upon a metal substrate and heat cured as in Example 1. The resulting coating demonstrates good gloss, good metallic orientation, good metal depth variation and good weathering resistance.

EXAMPLE 18

The procedure of Example 1 is repeated except for the differences: the coating of the aluminum flakes is prepared from 30 parts by weight of the same aluminum paste used in Example 1 (19.5 parts by weight aluminum) and 4.7 parts by weight of the thermosettable material, i.e., epoxy-functional copolymer of Example 1 and azelaic acid in the proportions used in Example 1, 0.4 parts by weight tetrabutyl ammonium bromide, and 0.03 parts by weight poly (lauryl acrylate).

The cured finish obtained has good physical properties and good depth variation in metal pigment positioning.

EXAMPLE 19

The procedure of Example 1 is repeated except for the differences that the coating of the aluminum flakes is prepared from 30 parts by weight of aluminum paste used in Example 1 (19.5 parts by weight aluminum) and from 2.93 parts by weight of the thermosettable material, i.e., epoxy-functional copolymer of Example 1 and azelaic acid in the proportions used in Example 1, 0.29 parts by weight tetrabutyl ammonium bromide, and 0.02 parts by weight poly (lauryl acrylate).

The cured finish obtained has good physical properties and good depth variation in metal pigment positioning.

EXAMPLE 20

The procedure of Example 1 is repeated except for the following differences: the coating of the aluminum flakes is prepared from 30 parts by weight of the aluminum paste used in Example 1 (19.5 parts by weight aluminum) and 1.76 parts by weight of the thermosettable material, i.e., the epoxy-functional copolymer of Example 1 and azelaic acid in the proportions used in Example 1, 0.18 parts by weight tetrabutyl ammonium bromide, and 0.01 parts by weight poly (lauryl acrylate) - M_(n) = 10,000.

The cured finish obtained has good physical properties and good depth variation in metal pigment positioning.

EXAMPLE 21

The procedure of Example 1 is repeated except for the following differences: the coating of the aluminum flakes is prepared from 30 parts by weight of the aluminum paste used in Example 1 (19.5 parts by weight aluminum) and 2.54 parts by weight of the thermosettable material, i.e., the epoxy-functional copolymer of Example 1 and azelaic acid in the proportions used in Example 1, 0.25 parts by weight tetrabutyl ammonium bromide, and 0.01 parts by weight poly (lauryl acrylate) - M_(n) = 10,000.

The cure finish obtained has good physical properties and good depth variation in metal pigment positioning.

EXAMPLE 22

The procedure of Example 1 is repeated except for the following differences: the coating of the aluminum flakes is prepared from 30 parts by weight of the aluminum paste used in Example 1 (19.5 parts by weight aluminum) and 0.39 parts by weight of the thermosettable material, i.e., epoxy-functional copolymer of Example 1 and azelaic acid in the proportions used in Example 1, 0.04 parts by weight tetrabutyl ammonium bromide, and 0.002 parts by weight poly (lauryl acrylate) - M_(n) = 10,000.

The cured finish obtained has good physical properties and good depth variation in metal pigment positioning.

EXAMPLE 23

The procedure of Example 1 is repeated except for the difference that a functionally equivalent amount of an epoxy-functional and hydroxy-functional copolymer of alpha-beta olefinically unsaturated monomers is substituted for the epoxy-functional copolymer of Example 1 and a functionally equivalent amount of poly (azelaic anhydride) is substituted for the azelaic acid. The epoxy-functional and hydroxy-functional copolymer used in this example is prepared from the below listed components in the manner hereinafter described:

                              Percent By Weight                                    Reactants       Grams     Of Total Reactants                                   ______________________________________                                         glycidyl methacrylate                                                                          225.0     15                                                   hydroxyethyl methacrylate                                                                      75.0      5                                                    butyl methacrylate                                                                             600.0     40                                                   styrene         75.0      5                                                    methyl methacrylate                                                                            525.0     35                                                   ______________________________________                                    

The above mentioned monomers are admixed in the proportions above set forth and 70.0 grams (4.5 percent based on the continued weights of reactants) of 2,2' - azobis - (2-methyl propionitrile), hereinafter called AIBN, are added to the monomer mixture. The solution is added dropwise over a 3 hour period into 1500 ml. toluene at 100° - 180°C. under nitrogen atmosphere. Then 0.4 grams of AIBN dissolved in 10 ml. of acetone are added over a 1/2 hour period and refluxing is continued for 2 additional hours.

The toluene-polymer solution is diluted in 1500 ml. acetone and coagulated in 16 liters of hexane. The white powder is dried in a vacuum oven at 55°C. for 24 hours. This copolymer has molecular weight - M_(w) - M_(n) = 6750/3400 and the molecular weight per epoxy group is about 1068.

The cured finish obtained from the aluminum pigmented powder of this example has good physical properties and the aluminum flakes demonstrate good orientation and good depth variation.

EXAMPLE 24

The procedure of Example 23 is repeated with the single difference that about 35 percent of the poly (azelaic anhydride) is replaced with a functionally equivalent amount of 12 - hydroxystearic acid.

EXAMPLE 25

The procedure of Example 1 is repeated except for the difference that an epoxy functional, amide-functional copolymer of alpha-beta olefinically unsaturated monomers is substituted for the epoxy functional copolymer of Example 1 and a functionally equivalent amount of a carboxy-terminated polymer is substituted for the azelaic acid. The epoxy-functional amide - functional copolymer used in this example is prepared from the below listed components in the manner hereinafter described:

                              Percent By Weight                                    Reactants      Grams      Of Total Reactants                                   ______________________________________                                         glycidyl methacrylate                                                                         45         15                                                   acrylamide     15         5                                                    butyl methacrylate                                                                            111        37                                                   methyl methacrylate                                                                           129        43                                                   ______________________________________                                    

The above mentioned monomers are admixed in the proportions above set forth and 110 grams of 2,2' - azobis - (2 - methylpropionitrile), hereinafter called AIBN, are added to the mixture. The mixture is slowly added to 200 ml. of toluene heated to 80° - 90° C. which is being stirred vigorously under a nitrogen atmosphere. A condenser is provided at the top of the toluene container to condense the toluene vapors and return the condensed toluene to the container. The monomer mixture is added through a regulating valve and the rate of addition is controlled to maintain a reaction temperature of 90° - 110°C. with the rest of the heat supplied from an external heater. After the addition of the monomer mixture is completed (3 hours), 0.8 gram of AIBN dissolved in 10 ml. acetone is added over a 1/2 hour period and refluxing is continued for 2 additional hours.

The resultant toluene-polymer solution is diluted with 200 mls. acetone and coagulated in 2 liters of hexane. The white powder is dried in the vacuum oven at 55°C. for 24 hours. Its molecular weight is determined to be M_(w) /M_(n) = 6700/3200 and WPE (molecular weight per epoxide group) is about 1000.

The carboxy terminated polymer to be used as crosslinking agent is prepared from the following materials in the following manner: five hundred grams of a commercially available epoxy resin, Epon 1001, (epoxide equivalent 450 - 525, melting range 64° - 76°C. - molecular weight average 900°C.), is charged into a 500 ml. stainless steel beaker having a heating mantle. The epoxy resin is heated to 110°C. As the epoxy resin is stirred, 194 grams of azelaic acid are added. After a reaction time of 30 minutes, a homogeneous mixture is obtained. The mixture resin only partially reacted, is poured into an aluminum pan and cooled. The solid mixture is pulverized to pass through a 100 mesh screen by use of a blender. This resin is only partially reacted because if fully reacted it could not be powdered. A portion of the carboxy terminated polymer is weighed out for making a powder coating composition in accordance with this invention.

The cured finish obtained from the aluminum pigmented powder of this example has good physical properties, and the aluminum flakes demonstrate good orientation and good depth variation.

EXAMPLE 26

The procedure of Example 1 is repeated except for the difference that a functionally equivalent amount of a hydroxyfunctional copolymer is substituted for the epoxy-functional copolymer of Example 1 and a functionally equivalent amount of hexamethoxy melamine is substituted for the azelaic acid.

The hydroxy-functional copolymer used in this example is prepared from the below listed components in the manner hereinafter described:

    Reactants            Parts By Weight                                           ______________________________________                                         2-hydroxyethyl methacrylate                                                                         15                                                        ethyl acrylate       25                                                        methyl methacrylate  60                                                        ______________________________________                                    

A one liter, four-necked flask which contains 150 ml. of methyl ethyl ketone is heated until the contents of the flask are at a refluxing temperature of 85°C. A mixture of the above listed monomers and 4 parts by weight of 2,2' - azobis - (2-methyl propionitrile), hereinafter called AIBN, in the total amount of 208 grams is added in a dropwise fashion over a period of one and a half hours to the reaction mixture which is maintained at 85°C. After the monomer addition is complete, 0.5 grams of AIBN (dissolved in 20 grams of toluene) is added dropwise. The refluxing is continued for an additional one-half hour to complete the polymerization.

The solution is poured into shallow stainless steel trays. These trays are placed in a vacuum oven and the solvent evaporated therefrom. As the solvent is removed, the copolymer becomes more concentrated. The temperature of the vacuum oven is raised to 110°C. Drying is continued until the solvent content of the copolymer is below 3 percent. The trays are cooled and the copolymer collected and ground to pass through a 20 mesh screen.

The cured finish obtained from the aluminum pigmented powder of this example has good physical appearance and the aluminum flakes are distributed with good orientation and depth variation.

EXAMPLE 27

The procedure of Example 1 is repeated except for the difference that a functionally equivalent amount of a self-crosslinking copolymer is substituted for the epoxy-functional copolymer and the azelaic acid.

The self-crosslinking copolymer used in this example is prepared from the following listed components in the manner hereinafter described.

    ______________________________________                                         Reactants              Grams                                                   ______________________________________                                         glycidyl methacrylate  30                                                      methacrylic acid       21                                                      methyl methacrylate    129                                                     butyl methacrylate     120                                                     ______________________________________                                    

The monomers above listed are mixed with 12 grams of an initiator, i.e., t-butylperoxypivate. Three hundred grams of benzene is charged into a one liter flask which is equipped with a dropping funnel. The flask is heated to 80°C. and a refluxing of the solvent is achieved. While maintaining the reaction temperature at 80°C., the monomer mixture is added in a dropwise fashion over a 2 hour period. After the addition is complete, the reaction is continued for another two hours. The contents of the flask are then cooled to room temperature. One hundred milliliters of the resultant solution are mixed with 0.3 grams of poly (2-ethylhexyl acrylate). The mixture is dispersed and then is dried in a vacuum over at 70°C. The powder coating obtained is ground to pass through a 200 mesh sieve.

The cured finish obtained from the aluminum pigmented powder of this example has good physical appearance and the aluminum flakes are distributed with good orientation and depth variation.

EXAMPLE 28

The procedure of Example 1 is repeated except for the difference that the poly (lauryl acrylate) is replaced with an equivalent amount of poly (butyl acrylate) - M_(n) = 9000.

EXAMPLE 29

The procedure of Example 1 is repeated except for the difference that the poly (lauryl acrylate) is replaced with an equivalent amount of poly (isododecyl methacrylate).

EXAMPLE 30

The procedure of Example 1 is repeated except for the difference that the poly (lauryl acrylate) is replaced with an equivalent amount of polyethylene glycol perfluoro octonoate (M_(n) =3400).

EXAMPLE 31

The procedure of Example 1 is repeated except for the difference that the principal film-forming material into which is mixed the encapsulated aluminum flakes is a thermoplastic powder coating material prepared from the following materials using the procedure hereinafter described.

    ______________________________________                                                            Parts By Weight                                             ______________________________________                                         poly (methyl methacrylate)                                                                          100                                                        M.sub.n = 40,000                                                              poly (lauryl methacrylate)                                                                          2                                                          M.sub.n = 120,000                                                             tetrabutylammonium bromide                                                                          0.05                                                      ______________________________________                                    

The above ingredients are mixed in a twin shell tumbling mixer for 10 minutes and then mill rolled at 190°C. for 15 minutes. The blend is cooled and pulverized to pass through a 200 mesh screen.

The above materials in the amount of 188 parts by weight are mixed with the yellow iron oxide pigment (8.26 parts by weight), phthalo green pigment (1.75 parts by weight) and 1.34 parts by weight of poly (lauryl acrylate).

A homogeneous mixture of the above is obtained by ball milling for 2 hours. This mixture is extended at 100°C. from a kneading extruder. The solid thus obtained is pulverized in an impact mill, i.e., an air classified impact mill, and sieved through a 200 mesh screen.

The aluminum pigmented finished coating thus prepared from these materials exhibits good aluminum particle orientation and depth variation.

EXAMPLE 32

The procedure of Example 1 is repeated with the single difference that the coated aluminum flakes are mixed with the principal film-forming powder in an amount such that they comprise 0.1 weight percent of the total powder paint composition.

EXAMPLE 33

The procedure of Example 1 is repeated with the principal film-forming powder in an amount such that they comprise 32.50 weight percent of the total powder paint composition.

EXAMPLE 34

The procedure of Example 1 is repeated with the single difference that the coated aluminum flakes are mixed with the principal film-forming powder in an amount such that they comprise 0.25 weight percent of the total powder paint composition.

EXAMPLE 35

The procedure of Example 1 is repeated with the single difference that the coated aluminum flakes are mixed with the principal film-forming powder in an amount such that they comprise 28.75 weight percent of the total powder paint composition.

EXAMPLE 36

The procedure of Example 1 is repeated with the single difference that the coated aluminum flakes are mixed with the principal film-forming powder in an amount such that they comprise 0.45 weight percent of the total powder paint composition.

EXAMPLE 37

The procedure of Example 1 is repeated with the differences that the coated aluminum flakes are the sole metal-pigment used and they constitute 10 weight percent of the total powder paint composition. In this example, non-metal pigments are not used.

EXAMPLE 38

The procedure of Example 1 is repeated with the differences that the coated aluminum flakes are the sole metal-pigment used and they constitute 1 weight percent of the total powder paint composition. In this example, the non-metal pigments constitute 21.9 weight percent of the total powder paint composition.

EXAMPLE 39

The procedure of Example 1 is repeated with the following compositional differences. The coated aluminum flakes are mixed with the principal film-forming powder in an amount such that they comprise 31.0 weight percent of the total powder paint composition and the principal film-forming powder contains, as the sole nonmetal pigment, phthalo green pigment in an amount such that it comprises 0.25 weight percent of the total powder paint composition.

EXAMPLE 40

The procedure of Example 1 is repeated with the following compositional differences. The coated aluminum flakes are mixed with the principal film-forming powder in an amount such that they comprise 4.0 weight percent of the total powder paint composition and the principal film-forming powder contains a mixture of metal-free pigments in an amount such that it comprises 22 weight percent of the total powder paint composition. The mixture of metal-free pigments consists predominantly of chrome yellow with flaventhron (yellow organic), red iron oxide and carbon black present from trace amounts to above one weight percent.

EXAMPLE 41

The procedure of Example 1 is repeated with the following compositional difference: The coated aluminum flakes are mixed with the principal film-forming powder in an amount such that they comprise 0.5 weight percent of the total powder paint composition.

EXAMPLE 42

A series of powder paints, A-E are prepared from the following materials in the manner hereinafter set forth and later electrostatically sprayed as in Example 1 for test purposes.

STEP I

The materials listed below are thoroughly mixed.

    __________________________________________________________________________                   A     B     C     D     E                                                      Parts By Weight                                                  __________________________________________________________________________     1.                                                                               aluminum paste                                                                 (65% metal) 30.00 30.00 30.00 30.00 30.00                                    2.                                                                               thermosettable                                                                 mixture     9.75  13.65 19.5  29.25 39.00                                      (a) resin*  8.58  12.01 17.16 25.74 34.32                                      (b) polyazelaic                                                                anhydride   1.17  1.64  2.34  3.51  4.68                                         % based on weight                                                              of aluminum                                                                              50.00 70.00 100.00                                                                               150.00                                                                               200.00                                   3.                                                                               poly(lauryl acrylate)                                                                      0.06  0.08  0.12  0.18  0.23                                     4.                                                                               tetrabutylammonium                                                                         0.45  0.63  0.9   1.125 1.8                                        bromide                                                                      5.                                                                               methylene chloride                                                                         250.00                                                                               250.00                                                                               250.00                                                                               250.00                                                                               250.00                                   __________________________________________________________________________      *epoxy--functional copolymer of Example 1.                               

STEP II

This mixture is then spray dried as in the preceding examples and a product comprising aluminum flakes encapsulated in a thermosettable mixture of resin and crosslinking agent is obtained wherein the relative weights of the components are as follows:

                  A    B    C    D     E                                                         Parts by Weight                                                  __________________________________________________________________________     1.                                                                               aluminum flakes                                                                            19.5 19.5 19.5 19.5  19.5                                        2.                                                                               thermosettable mixture                                                                     9.75 13.65                                                                               19.50                                                                               29.25 39.00                                       3.                                                                               poly (laurylacrylate)                                                                      0.06 0.08 0.12 0.18  0.23                                        4.                                                                               tetrabutylammonium                                                             bromide     0.45 0.63 0.9  1.125 1.8                                         __________________________________________________________________________

STEP III

These encapsulated aluminum flakes are sieved through a 44 micron screen. All particles left on the screen are rejected.

STEP IV

A non-metallic powder mixture is made up by thoroughly mixing the below listed materials after which the mixture is pulverized and sieved through a 75 micron screen. All particles left on the screen are rejected.

    __________________________________________________________________________                   A     B     C     D     E                                                      Parts by Weight                                                  __________________________________________________________________________     1.                                                                               resin*      166   166   166   166   166                                      2.                                                                               azelaic acid                                                                               22.64 22.64 22.64 22.64 22.64                                    3.                                                                               poly(laurylacrylate)                                                                       1.34  1.34  1.34  1.34  1.34                                     4.                                                                               Pigments                                                                       (a) thalo green                                                                            2.03  2.03  2.04  2.06  2.08                                       (b) yellow iron oxide                                                                      8.04  8.07  8.11  8.18  8.25                                     __________________________________________________________________________      *epoxy--functional copolymer of Example 1                                

STEP V

An evenly mixed blend is formed from the encapsulated aluminum flakes of Step III and the nonmetallic powder mixture of Step IV in the following relative proportions:

                  A     B     C     D     E                                                      Parts by Weight                                                  __________________________________________________________________________     1.                                                                               encapsulated aluminum                                                                      2.255 2.256 3.009 3.764 4.518                                      flakes                                                                       2.                                                                               nonmetallic powder                                                                         97.745                                                                               97.444                                                                               96.991                                                                               96.236                                                                               95.482                                   __________________________________________________________________________

The relative concentrations of ingredients in each of these blends are essentially the same.

The powders thus obtained are sprayed on electrically grounded substrates and baked as in Example 1. Aluminum pigment spacing and orientation is best when the resin encapsulation on the aluminum flakes is in the range of 50 to 70 weight percent of the aluminum with the very best achieved with paint A (50 weight percent encapsulation based on the weight of aluminum flakes).

EXAMPLE 43

Aluminum flakes are encapsulated as in Example 1 except for the differences that solvents other than methylene chloride, i.e., toluene, xylene, acetone, hexane and methyl ethyl ketone, are used to disperse the film-forming material and aluminum flakes prior to spray drying. The spray drying operation is adjusted in conformance with the relative volalities of the solvent used in each test. The encapsulated flakes thus prepared are incorporated into the powder paint of Example 1, electrostatically sprayed upon substrates and the substrates are baked as in Example 1.

Hydrocarbons, alcohols, and ketones boiling in the range of 50°C. to 152°C., preferably 50°C. to 90°C., can be used for this purpose. The amount of solvent used is in excess of the combined weights of the aluminum flakes and the film-former used for encapsulation. Advantageously, the amount of solvent used is in the range of about 3 to 100 times the combined weights of film-former and aluminum flakes.

Apparatus and methods for electrostatically spraying powder coating materials are illustrated and described in U.S. Pat. Nos. 3,536,514; 3,593,678; and 3,598,629.

The term "copolymer" is used herein to mean a polymer formed from two or more different monomers.

Many modifications of the foregoing examples will be apparent to those skilled in the art in view of this specification. It is intended that all such modifications which fall within the scope of this invention be included within the appended claims.

The disclosures of U.S. Pat. application Ser. No. 442,291 filed Feb. 12, 1974 by Santokh S. Labana et al and entitled "Powder Coating Compositions Including Glycidyl Ester-Modified Copolymer" are incorporated herein by reference.

Any and all disclosures appearing in the claims and not specifically appearing in the body of this specification are herewith incorporated in the body of this specification. 

We claim:
 1. In a powder paint which exclusive of catalysts, antistatic agents, plasticizers and flow control agents, the same being known and optional additives to powder paints, consists essentially of aluminum flakes, non-metal pigment and a particulate, organic, film-former, the improvement whereinA. said non-metal pigment comprises 0 to about 22 weight percent of said powder paint, B. said aluminum flakes comprise about 0.005 to about 25 weight percent of said powder paint and are encapsulated prior to admixture with said particulate, organic, film-former with about 2 to about 200 parts by weight of a continuous coating of a thermosettable, organic, film-former per 100 parts by weight aluminum flakes, said thermosettable, organic, film-former consisting essentially of a copolymer having average molecular weight (M_(n)) in the range of about 1500 to about 15,000 and glass transition temperature in the range of about 40°C. to about 90°C., bearing functional groups provided by constituent monomers selected from the group consisting of glycidyl esters of a monoethylenically unsaturated carboxylic acid, C₅ - C₇ monohydroxy acrylates, C₅ - C₇ monohydroxy methacrylates and alpha-beta olefinically unsaturated amides and wherein at least above 50 weight percent of the constituent monomers are selected from acrylic monomers and the remainder weight percent, if any, of the constituent monomers consists essentially of C₈ - C₁₂ monovinyl hydrocarbons said copolymer being self-crosslinkable or employed in combination with a monomeric or polymeric crosslinking agent that is capable of reacting with said functional groups on said copolymer and containing about 0.05 to about 20 parts by weight of an ammonium salt selected from the group consisting of tetraalkylammonium halides and substituted tetraalkylammonium halides wherein at least one alkyl radical is replaced with an aryl, phenoxy or alkoxy radical per 100 parts by weight of said thermosettable, organic, film-former, and C. said particulate, organic, film-former is selected from the group consisting of1. a thermoplastic, particulate film-former that is a polymer of alpha-beta olefinically, unsaturated monomers of which about 51 to about 100 weight percent are acrylic monomers and 0 to about 49 weight percent are monovinyl hydrocarbons, and
 2. thermosettable, particulate, film-formers consisting essentially of a copolymer having average molecular weight (M_(n)) in the range of about 1500 to about 15,000 and glass transition temperature in the range of about 40°C. to about 90°c., bearing functional groups provided by constituent monomers selected from the group consisting of glycidyl esters of a monoethylenically unsaturated carboxylic acid, C₅ - C₇ monohydroxy acrylates, C₅ - C₇ monohydroxy methacrylates and alpha-beta olefinically unsaturated amides and wherein at least about 50 weight percent of the constituent monomers are selected from acrylic monomers and the remainder weight percent, if any, of the constituent monomers consists essentially of C₈ - C₁₂ monovinyl hydrocarbons, said copolymer being self-crosslinkable or employed in combination with a monomeric or polymeric crosslinking agent that is capable of reacting with said functional groups on said copolymer.
 2. A powder paint in accordance with claim 1 wherein said ammonium salt is a tetraalkylammonium halide in which the alkyl radicals contain 1 to 4 carbon atoms.
 3. A powder paint in accordance with claim 1 wherein said encapsulation of said aluminum flakes is in the amount of about 30 to about 70 parts by weight of said thermosettable, organic, film-former per 100 parts by weight of said aluminum flakes.
 4. A powder paint in accordance with claim 1 wherein said encapsulation of said aluminum flakes is in the amount of about 2 to about 30 parts by weight of said thermosettable, organic, film-former per 100 parts by weight of said aluminum flakes.
 5. A powder paint in accordance with claim 1 wherein a portion of said encapsulated aluminum flakes are replaced with nickel powder, said portion being in an amount such as to provide a nickel powder to encapsulated aluminum flake weight ratio of about 1.5:1 to about 2.5:1.
 6. A powder paint in accordance with claim 1 wherein said powder paint also contains a flow control agent which comprises between about 0.05 and about 4.0 weight percent of said powder paint and is a polymer having average molecular weight (M_(n)) of at least 1000, and having, at the baking temperature of the powder paint a lower surface tension than the surface tension of said particulate, organic, film-former, and being a polymer or copolymer selected from the group consisting of acrylate esters, methacrylate esters and polyethylene or polypropylene glycol esters of fluorinated fatty acids, polymeric siloxanes and polymeric halogenated siloxanes.
 7. A powder paint in accordance with claim 1 wherein said aluminum flakes are encapsulated by dispersing 100 parts by weight of said aluminum flakes and about 10 to about 200 parts by weight of said thermosettable, organic, film-former in a volatile solvent boiling in the range of about 40°C. to about 152°C. that is fugitive from said thermosettable, organic, film-former and said aluminum flakes in spray drying and spray drying said dispersion, said solvent being present in said dispersion in excess of the total amount of said aluminum flakes and said film-former.
 8. A powder paint in accordance with claim 1 wherein said 100 parts by weight of said aluminum flakes is dispersed in said solvent with about 30 to about 70 parts by weight of said thermosettable, organic, film-former, said solvent is selected from methylene chloride and alcohols, ketones and hydrocarbons boiling in the range of about 50°C. to about 90°C. and is present in said dispersion in an amount at least 3 times the combined amounts of said aluminum flakes and said film-former.
 9. A powder paint in accordance with claim 1 wherein said aluminum flakes are encapsulated in a thermosettable, organic, film-former consisting essentially of a copolymer of monoethylenically unsaturated monomers of which about 5 to about 20 weight percent of the constituent monomers are glycidyl esters of a monoethylenically unsaturated carboxylic acid, in excess of 50 weight percent of the constituent monomers are acrylic monomers and the remainder weight percent, if any, of the constituent monomers consist essentially of C₈ - C₁₂ monovinyl hydrocarbons, and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids.
 10. A powder paint in accordance with claim 1 wherein said particulate, organic, film-former consists essentially of a copolymer of monoethylenically unsaturated monomers of which about 5 to about 20 weight percent of the constituent monomers are glycidyl esters of a monoethylenically unsaturated carboxylic acid, in excess of 50 weight percent of the constitute monomers are acrylic monomers and the remainder weight percent, if any, of the constituent monomers consist essentially of C₈ - C₁₂ monovinyl hydrocarbons, and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids.
 11. A powder paint in accordance with claim 1 wherein said particulate, organic, film-former is a thermoplastic, particulate, organic, film-former and has average molecular weight (M_(n)) in the range of about 30,000 to about 80,000 and a glass transition temperature in the range of about 60°C. to about 110°C.
 12. A powder paint in accordance with claim 1 wherein said particulate, organic, film-former contains about 0.05 to about 0.15 weight percent of an ammonium salt selected from the group consisting of tetraalkylammonium halides and substituted tetraalkylammonium halides wherein at least one alkyl radical is replaced with an aryl, phenoxy or alkoxy radical.
 13. A powder paint in accordance with claim 1 wherein said copolymer of said particulate, organic, film-former bears functional groups provided by constituent monomers which are selected from C₅ - C₇ monohydroxy acrylates and C₅ - C₇ monohydroxy methacrylates and is employed with a melamine crosslinking agent.
 14. A powder paint in accordance with claim 1 wherein said aluminum flakes are encapsulated in a thermosettable, organic, film-former consisting essentially of a copolymer of about 5 to about 20 weight percent of a glycidyl ester of a monoethylenically unsaturated carboxylic acid and about 80 to about 95 weight percent of esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acid and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids.
 15. A powder paint in accordance with claim 1 wherein said aluminum flakes are encapsulated in a thermosettable, organic, film-former consisting essentially of a copolymer of about 5 to about 20 weight percent of a glycidyl ester of a monoethylenically unsaturated carboxylic acid, about 2 to about 10 weight percent of a C₅ - C₇ hydroxy acrylate or methacrylate and about 70 to about 93 weight percent of esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acid and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids.
 16. A powder paint in accordance with claim 1 wherein said aluminum flakes are encapsulated in a thermosettable, organic, film-former consisting essentially of a copolymer of about 5 to about 20 weight percent of a glycidyl ester of monoethylenically unsaturated carboxylic acid, about 2 to about 10 weight percent of an alpha-beta olefinically unsaturated amide and about 70 to about 93 weight percent of esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acid and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids.
 17. A powder paint in accordance with claim 16 wherein said alpha-beta olefinically unsaturated amide is selected from the group consisting of acrylamide and methacrylamide.
 18. A powder paint in accordance with claim 1 wherein said thermosettable, organic, film-former used to encapsulate said aluminum flakes contains about 0.05 to about 12 parts by weight of said ammonium salt per 100 parts by weight of said thermosettable, organic, film-former.
 19. A powder paint in accordance with claim 1 wherein said thermosettable, organic, film-former used to encapsulate said aluminum flakes contains about 0.05 to about 10 parts by weight of said ammonium salt per 100 parts by weight of said thermosettable, organic, film-former.
 20. A powder paint in accordance with claim 1 wherein said particulate, organic, film-former consists essentially of a copolymer of about 5 to about 20 weight percent of a glycidyl ester of a monoethylenically unsaturated carboxylic acid and about 80 to about 95 weight percent of esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acid and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids.
 21. A powder paint in accordance with claim 1 wherein said particulate, organic, film-former consists essentially of a copolymer of a monoethylenically unsaturated carboxylic acid, about 2 to about 10 weight percent of a C₅ - C₇ hydroxy acrylate or methacrylate and about 70 to about 93 weight percent of esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acid and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids.
 22. A powder paint in accordance with claim 1 wherein said particulate, organic, film-former consists essentially of a copolymer of about 5 to about 20 weight percent of a glycidyl ester of a monoethylenically unsaturated carboxylic acid, about 2 to about 10 weight percent of acrylamide or methacrylamide and about 70 to about 83 weight percent of esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acid and a crosslinking agent selected from the group consisting of dicarboxylic acids and anhydrides of dicarboxylic acids. 